1. Field of Disclosure
The present disclosure relates generally to image processing in image processing devices such as video cameras and still cameras, and more specifically to efficient determination of an illuminant of a scene in such devices.
2. Related Art
A scene refers to any area/object, the image of which is sought to be captured using an image capture device. An image capture device (ICD) in turn refers to a device such as a still camera or a video camera which is designed to receive light signals from a scene and represent the corresponding image in a suitable format (analog or digital).
In general, light (“incident light”) originating from a light source (e.g., Sun, light bulb, reflection from an object) is incident on a scene, and emanates from the scene due to interactions with the objects present in the scene. The interactions include acts such as reflection, absorption, dispersion, diffraction, etc., as is well known in the arts. Some times, a light source itself may be part of a scene. The light (“received light”) from the scene is eventually received at an ICD and the image of the scene is captured as an image frame.
The nature of incident light generally depends on various factors such as any intervening medium (e.g., clouds, glass) present between a light source and a scene, the colors and their brightness with which the light source/light sources generate light, etc. Incident light generally is a combination of different colors of same/different brightness. Thus, the incident light has brighter characteristics on clear-sky days in comparison to cloudy situations.
The general type of light incident on a scene is referred to as an illuminant, which is typically dependent on the light source/light sources as well as the factors noted above. Such illuminant is henceforth referred to as “actual illuminant” to differentiate from “potential illuminants” described in the sections below.
There is often a need to determine an actual illuminant of a scene by examining the image of a scene. For example, in an ICD, there are various corrections that may need to be performed based on a determination of actual illuminant. Auto-white balance (AWB) correction is one such example.
As is well known in the relevant arts, AWB correction generally refers to a color correction that may need to be performed on image representation, with the nature of correction depending on the actual illuminant. Often the AWB correction parallels the correction that human eye often performs depending on different illuminants based on which light is received.
One approach to determining an actual illuminant is to store (in an ICD) data representing how a color in a scene would be represented (in the received light) under various illuminants (pre calibrated colors called as reference colors), and comparing the image content for match with these reference colors. Such approaches often require substantial processing resources.
In general, there is a need to reduce the computational complexity (or resource requirements, in general) in determining the actual illuminants, without possibly compromising accuracy at least substantially.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.